Digital Phenotypes for Predicting Depression

Inclusion Criteria for Patient Group: 1. Adults aged 19 to 75 years and 11 months. 2. Diagnosed with a major mood disorder (bipolar I or II disorder, or major depressive disorder) based on DSM-5, with a history of psychiatric visits for mood symptoms. 3. Has experienced at least one prior depressive episode (major, minor, or brief). 4. Owns a smartphone with stable internet connectivity, can operate it without difficulty, and agrees to install a digital phenotyping application, wear a Fitbit device daily, and complete daily mood logs throughout the study period. Inclusion Criteria for Healthy Control Group: 1. Adults aged 19 to 75 years and 11 months. 2. No current or past diagnosis of bipolar disorder or major depressive disorder. 3. Scores below clinical thresholds on both K-MDQ (\<7) and PHQ-9 (\<5) at baseline assessment. 4. Owns a smartphone with stable internet connectivity, can operate it without difficulty, and agrees to install a digital phenotyping application, wear a Fitbit device daily, and complete daily mood logs throughout the study period. Inclusion Criteria for Hight Risk Group: 1. Adults aged 19 to 75 years and 11 months. 2. No current or past diagnosis of bipolar disorder or major depressive disorder. 3. Meets either of the following: A. Scores above the threshold on K-MDQ (≥7) or PHQ-9 (≥5) at baseline. B. Reports persistent mood symptoms during MINI (e.g., ≥2 weeks of depressive mood/anhedonia, or several days of elevated/irritable mood). 4. Owns a smartphone with stable internet connectivity, can operate it without difficulty, and agrees to install a digital phenotyping application, wear a Fitbit device daily, and complete daily mood logs throughout the study period. Exclusion Critera (Overall) 1. Inability to provide informed consent due to cognitive impairment, severe psychiatric symptoms, or language barriers. 2. Presence of any neurological or medical condition that may significantly affect mood, cognition, or behavior (e.g., epilepsy, dementia, traumatic brain injury). 3. Current substance use disorder or dependence (excluding nicotine or caffeine) that is either untreated or clinically unstable. 4. Severe suicidal ideation or risk as determined by clinical judgment at screening. 5. Ongoing participation in another interventional clinical trial, particularly those involving psychotropic medications or digital health interventions. 6. Inability or unwillingness to wear a wearable device (Fitbit) or use the required mobile application daily throughout the study. 7. Lack of stable internet access or a compatible smartphone required for digital phenotyping data collection. 8. Any other condition that, in the investigator's judgment, may compromise the participant's safety, compliance, or the integrity of the study data.